erty (as long as the site is level and receives plenty
of light). While initially more expensive than an at-
tached greenhouse, they provide a lower cost per
plant, since so many more plants can be grown in
them.
In most areas across the country, a freestanding
greenhouse will allow you to start plants much ear-
lier in the growing season (January or February) and
then, at first sign of frost, you can bring your plants
in again to extend the growing season through Octo-
ber or November. Here in Montana, a separate heat-
ing system is required for year-round operation.
Freestanding greenhouses have the added advan-
tage of being a sanctuary away from home; a relaxing
place that you can go to get away for a while. A place
where no phones exist and you are surrounded only
by the beauty of the flowers and plants that you are
growing.
Glazing
Glazing is the covering around the greenhouse
frame. It is responsible for letting sunlight and its
warmth in while keeping the elements out. Glass is
the best glazing material, but it is also the most ex-
pensive. Plastic sheeting works well and is inexpen-
sive but will deteriorate quickly. Polycarbonate is less
expensive than glass, is lightweight, and retains heat
better than both glass or plastic. Additionally, poly-
carbonate can be used on flat or bent surfaces, trans-
mits light well, and is extremely strong.
Site Selection
The closer to the house or garden a greenhouse
is located, the more you are likely to use it. Also,
consider access to electricity and water — both of
which you’ll probably need. Look for a level area
with maximum exposure to the sun. If possible, find
a location where the greenhouse will be getting at
least 6 hours of direct sunlight per day during the
winter. By orienting the greenhouse east to west, the
largest side will get full southern sun exposure. If
you don’t have an area with enough sun, grow lights
can be added to compensate.
Deciduous trees can provide needed shade in the
summer, but since they lose their leaves each fall,
they allow for sunlight in the winter. Avoid select-
ing a greenhouse site near coniferous trees or other
objects that will cast a shadow during long winter
months. A greenhouse can be placed on almost any
surface, but there should be adequate drainage. To
create an ideal surface, lay a layer of landscape cloth
over the area to be used — this will keep the weeds
out, but allow for drainage — and cover the cloth
with 3 inches of 1/4-inch gravel.
Accessories
In addition to the frame of the greenhouse, there
are many accessories that can go inside. Depending
June 2018
on your commitment and budget, you can add shelv-
ing, a mist system, a heating system, a fan, a tool
rack, a potting bench and the list goes on. Consider
what you really need, what you’d like to have and
what you have room for.
Environmental Control
Heating
If you live in a cold climate you may need to
insulate your greenhouse to help keep plants warm.
While a lot of sun will come in during the day, an un-
insulated greenhouse will cool off quickly at night. In
this case, a heating system may be needed.
A 220-volt circuit electric heater works well.
Small gas or oil heaters designed to be installed
through a masonry wall are also effective. There are
also solar heaters designed specifically for green-
houses. Radiant heat lamps hung over plants com-
bined with soil heating cables under plants will keep
most plants warm enough. Be sure the greenhouse
is vented and that whatever heating system you have
has an automatic shut-off. Placing rocks or barrels of
water inside the greenhouse to capture the suns heat
and keep plants warm during cool evenings.
Ventilation
Plants can get too hot even during cold or cool
weather, so good greenhouse ventilation is crucial.
Vents can be hand cranked, but temperatures need
to be monitored closely. There are electric and tem-
perature-sensitive hydraulic vents that automatically
open and close. Installing an oscillating fan will help
keep air moving through the greenhouse and prevent
many disease problems.
Shading
In warmer environments or when the sun is
directly hitting the greenhouse, shading can keep
plants from getting burned by reducing the amount
of summer sunlight. Polypropylene shade cloth, roll-
up screens of wood or aluminum, vinyl plastic shad-
ing, or paint-on materials can all be used to shade
plants.
Pests
Keeping a greenhouse and gardening tools clean
is the first step in avoiding pest problems. Check
plants before bringing them into the greenhouse
carefully to be sure they are bug and disease-free. If
cleanliness fails, immediately remove any plants with
bugs or diseases. Spraying plant foliage with an in-
sect killing soap will kill or deter many insect pests.
Also, bring “good bugs” in to eat the “bad bugs.” GG
Eric Vinje is the owner of Planet Natural. You can visit his
website at PlanetNatural.com.
www.GardenandGreenhouse.net
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